阅读理解。 Do you get enough sleep? With so much homework it's often difficult to get the rest you need. But you need to try, because sleep keeps you healthy and it stops you getting fat. Recently, a group of U. S. scientists did a study (研究) of kids aged between 8 and 13. The study found that if kids sleep for just one extra (额外的) hour each day, the chance of their getting fat is cut by about 30 percent. Why? When people don't get enough sleep, they become tired. When they are tired, they don't exercise enough. Also, kids like snacks. If they are awake (醒着的) an extra hour or two each day, they have more time to eat snacks or other unhealthy foods. So, how much sleep should you get? Scientists suggest 10 to 11 hours a night for kids aged 5 to 12. For older kids, eight to nine hours will do. 1. How many reasons are given why people might get fat without enough sleep? A. 3. B. 2. C. l. D. None. 2. If you are under 10, how long do the scientists advise you to sleep? A. 10 to 11 hours. B. 8 to 9 hours. C. 8 to 13 hours. D. As long as possible. 3. Where was the study done by the scientists? A. In China. B. In Britain. C. In America. D. In Japan. 4. What does 'eight to nine hours will do' mean? A. Eight to nine hours' sleep will be good and enough. B. Eight to nine hours' sleep will be too long. C. Eight to nine hours' sleep will help get fat. D. Eight to nine hours' sleep will help eat snacks and unhealthy foods. 5. What does the passage talk about? A. How to get long sleep. B. How to keep fat. C. Enough sleep makes people healthy and slim (苗条). D. Long sleep makes people healthy and slim.